Ruby中的普通变量与实例变量,有什么区别? [英] Normal Variables Vs Instance variable in Ruby, Whats the difference?
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问题描述
考虑以下示例 ruby 类
Consider the following sample ruby class
class User
def hello
puts "hello"
end
end
现在,进行初始化.有两种方式
now, for initialization. there are two ways
正常变量
1.9.3p125 > tr = User.new
=> #<User:0x98778c4>
1.9.3p125 > tr.hello
Hello world
=> nil`
实例变量:
1.9.3p125 > @tr = User.new
=> #<User:0x9890f2c>
1.9.3p125 > @tr.hello
Hello world
=> nil
现在,在这两种情况下,它的工作原理相同.那么普通变量和实例变量有什么区别?
Now, in both cases it works the same. so what is the difference between normal variable vs instance variable?
推荐答案
普通变量仅在当前上下文中具有作用域;一个实例变量在类的一个实例中具有作用域.在您的情况下,他们感到困惑,因为上下文是 main
,它充当 Object
的实例.
A normal variable has scope only within the current context; an instance variable has scope throughout one instance of a class. In your case they're confused because the context is main
, which acts as an instance of Object
.
考虑以下内容,这可能会使事情更清楚
Consider the following, which may make things clearer
class User
def set_name
@name = "Bob"
surname = "Cratchett"
end
def hi
puts "Hello, " + @name
end
def hello
puts "Hello, Mr " + surname
end
end
irb(main):022:0> u = User.new
=> #<User:0x29cbfb0>
irb(main):023:0> u.set_name
irb(main):024:0> u.hi
Hello, Bob
=> nil
irb(main):025:0> u.hello
NameError: undefined local variable or method `surname' for #<User:0x29cbfb0 @name="Bob">
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